Process of producing water-insoluble petroleum-soluble carboxylic acids and the product thereof



Octe 20, 19311.

A. W. PROCESS OF PRODUGING WATER INSOLUBLE PETROLEUM SOLUBLE BURWELL 1,828,356

CARBOXYLIC ACIDS AND THE PRODUCT THEREOF Filed Dec. 20, 1926 C 02. lvz, ua/a/e amb/5 and keyhnes Lfd awo: nage.

- Patented ctQZO, 1931 UNITED STATES PATENT ori-luca ARTHUR W. BUB'WELL, OF NIAGARA FALLS, NEW YORK, ASSIGNOR TO ALOX CHEMICAL CORPORATION, OF NEW YORK, N. Y., A CORPORATION 0F NEW YORK PROCESS OF PRODUCIN G WATER-INSOLUBLE PETROLEUM-SOLUBLE CARBOXYLIC ACIDS AND THE PRODUCT THEREOF Application led December 20, 1926. Serial No. 156,053.

This invention relates to products particularly adapted for use in coating compositions containing nitrocellulose and to the process of making thesame.

In the preparation of artificial leather compositions, it is customary to spread upon a fabric base a coating composition comprising a solution of nitro-cellulose in ethyl acetate, butyl acetate or other suitable solvent, to-

0' gether with diluents such as, fori example,

benzol, alcohol, gasoline or the like, pigments and other fillers, and an oil or oils of the nature of castor oil. The benzol, alcohol, and gasoline are used as .diluents as they. alone are not solvents for nitro-cellulose. The oil or oils present in the compositionyhave the property of softening, or altering the physical characteristics of, the nitrocellulose whereby the dry coating, obtained upon evap. oration of the volatile solvents and dilu'ents,

4remains soft and flexible. l,

The relatively high cost of castor oil precludes the use of this softening agent in many instances, and substitutes therefor havebeen sought. For example, it has been attempted to substitute for castor oil the so-calledblown oils. The chief drawbacks the use of blown oils are their powerful rancid odor and the fact that they can only be incorporated iny articial leather compositions in somewhat restricted pared with"`c'astor oil.

' An Io'bjectjof the present invention is to pro- 10 vide a softening'agent for compositionscone.

taining nitro-.cellulose which may be incorp1 o rated in such' compositions in almost .un're-A stricted proportions, is more economical in cost than castor oil, and is practically free from objectionable odor. The invention has particular application-to the. production of artificial leather 'compositions I have found that, bythe li dation, under controlled c'onditlons, of hydrocarbons or mixtures thereof such as those oc- E curring inv petroleum oils, there may b tained organic carboxylic acid productsffi'o which a valuable softening agent'ma beo'b tained, which softening agent is equa and, many cases superior, 'to castor oil in coatin compositions containing nitro-cellulose.

proportions as com-y l More particularly, the ypresent Iinvention concernsv the saponiliable `carboxylic acid products obtained by the controlled oxidation of mid-continent or Pennsylvania petroleum distillates having a density of from about to 40 Baume, although I have found that these acid products are'obtainable from other: petroleum distillates than those just mentioned. f'

The process of making these saponifiable carboxylic acid products consists generally in the liquid-phase oxidation of hydrocarbons or mixturesl thereof, including l both starting material petroleum distillates having densities of approximately 1180-439 Baume vat 16 C. Especially suitable is the 45 Baum distillate knownas kerosene. This particular petroleum fraction has a distillation' range substantially as follows: l

. Distlllate s Tine am l Temp. C. mln.

173.0 181.0 2 181.5 5 191.0 8 196.5 5 197.5 5 6 0. 205.0 70. 209.5 so. 212.0 7 00. 220.0 5 100 423.0 4 110..' .15 7 120. .5 4 130-. 0 5 140. 240.01 e 150- .i 250.0 s 160.-.- 265.0 6 170.--- 267.0 8 180. 276.0 6 190. 297,0 5 4200.-

when@pffolifdisuua of the' above -ypeand character is subjected-to oxidation t ns, there are formed saponifiable, water- @the liquid phase, under controlled condif without the presence of Water-soluble carboxylic acids of relatively low molecular weight. The water-insoluble carboxylic acid bodies may be removed from the solution by various methods, as for example, by treating the solution comprising the said acid bodies and unoxidized petroleum distillate with an aqueou-s solution of an alkali, thus forming alkalimetal soaps of the said acids, separating the soaps from the unoxidized material, decomposing the soaps by treatment with a suitable acid, and isolating the thus purified and liberated acids.

The invention will be described and illus- 4trated hereinafter by reference to a batch process. It is to be understood, however, that the procedure may be made continuous, as shall be explained.

In' the accompanying drawing there is shown diagrammatically one form of apparatus suitable for use in carrying out the process of the invention. Y

The oxidation step proper takes place in an upright cylindrical reaction vessel o r oxidizer 1, which may be, for example, about 5 feet in diameter and about 16 to 18 feet in height. The oxidizer 1 may be made of any suitable Vmaterial such as iron or steel and should be capable of withstanding pressures up to 350 pounds per square inch. Preferably, the oxidizer 1 should be made of or lined with material which is resistant to the corrosive action of the reaction mixture; for example, provided with an inner shell of raluminum 2. The oxidizer is provided at a point near its lower end with 'a tight coil 3 which serves as a heating or cooling coil as required. Suitable means, not illustrated, such as a jacket surrounding-the oxidizer, also may be used to control the temperature of the oxidation reaction. At a point between the lower end of the oxidizer 1 and the tight coil 3 is an air spray pipe 4 connected by pipe line 5 to an air compressor 6. spray pipe 4 is so designed that air is ejected from it in the form of fine bubbles. 7, 8 and 9 are-a valved hydrocarbonfsupply pipe, a valved liquid discharge pipe and a valved gas discharge pipe, respectively. 10 is a pressure gauge, and 11 is a thermometer. 12 is a separating tank fed by the valved liquid discharge pipe 8 leading from the oxidizer 1; said tank bein provided with agitating means (not shown?.

From the bottom of the separating tank 12 extend the valved conduits 13 and 13 for the transference of fluids to the acid precipitating tank 17 and to the petroleum distillate supply tank 14, respectively. The tank 17 may e of any suitable material V(e. g. of lead) adapted to withstand the cdrrosive action of strong acids. 15 and 16 are valved supply pipes for conducting water and sodiv'120 C. or higher,

insoluble carboxylic acid bodies which are um hydroxide solutions respectively tothe soluble in the petroleum distillate, with or separating tank 12. 18 is a valved supply pipe for conducting sulfuric acid to the tank 17. The valved discharge line 19 leads to waste and the valved discharge line 19 leads to the still 20 which is provided with the valved discharge conduit 21. 22 is a condenser, 23 is a distillate receiver and 24 is a vacuum pump. l

The process is carried out in the apparatus illustrated as follows:

A petroleum hydrocarbon oil, such as, for example, the 45 Baume distillate above described, is charged into oxidizer 1, a small amount of an oxidizing catalyst or exciter of oxidation such as a compound of manganese copper or iron, say manganese oleateamounting to about 0.1 percent of the weight of the oil is added 'and the mixture heated up to a temperature in the neighborhood of preferably to about 135-140 C., and an oxidizing gas, preferably air, is supplied through the spray pipe 4. Gases are permitted to accumulate in the oxidizer until the desired pressure is reached, after which the pressurel is maintained or. regulated -by controlling the discharge of gases through the valved gas discharge pipe 9. The pressure may vary considerably, say from 150 to 350 pounds per square inch. The preferred pressure will depend upon a number of conditions, including the temperature maintained, the kind of hydrocarbon mixture under treatment, the rate of air supply and, if oxygen-enriched air is used, upon the richness of the oxygen supply. It is preferred to carry out the oxidation process under such conditions' that the reaction is substantially self-sustaining. In general, the reaction is self-sustaining at a temperature of about 135-'140 C., and at a pressure of about 250 Air served at a. temperature as low as 100 C.;

it is more rapid above 120 C., and the temperature may be allowed to rise to 155 C. with satisfactor results under some circum stances. There ore, while I prefer'to carry out the oxidation process at a temperature at which the reaction rate is fairly rapid, say 135-140 C., it is to be understood that the invention includes the employment of all suitable temperatures at Awhich oxidation takes place.'

During .the oxidizing treatment, as is stated above, gases collecting in the upper end of oxidizer 1 are released through the pipe 9. These gases contain practically no oxygen, butdo contain carbon dioxide, nitrogen and varying quantities of volatile acids, ketones-and other products of the oxidation.

ucts may be condensed in a suitable condenser pounds having (not shown) and .further treated for the recovery of formic acid, mixed light ketones, etc.

During the course'of the treatment of the petroleum distillate in the oxidizer 1, there appear to be formed, during the earllest stages of oxidation, formic acid and hi h molecular weight ketonic and/or aldehy ic bodies; continued oxidation results in the production of saponifiable carboxylic acids soluble in' the petroleum hydrocarbons and having molecular weights approximately one and one-half times those which would .naturally be calculated for acids derived from the original (i. e. unoxidized) h drocarbons, Prolonged oxidation converts t ese petroleum-soluble carboxylic acids into petroleuminsoluble hydroxy-carboxylic acids having about the same molecular weights as those which would naturally be calculated for acids derived from the original-hydrocarbons, low 'molecular-weight ketonicy and/or aldehydic bodies, and additional amounts of formic acid. For the purposes of the present invention it is desirable to continue the oxidation treatment until the maximum amount of the saponiiable, high molecular Weight, carboxylic acids soluble in the petroleum hydrocarbons has been obtained .while avoiding the formation. of petroleum-insoluble hydroxycarboxylic acids. The formationof the latter-named compounds depends upon several factors, principally the presence, or absence, in the starting material, of crystallizable bodies (e. g. wax) and hydrocarbon coma high molecular weight. That is to say, the higher the percentage of non-crystallizable bodies y composing the starting material (i. e. petroleum hydrocarbon mixtures), and the lower the molecular weights of thesel bodies, the more prone this starting material is to form petroleum-insoluble hydroxy-carboxylic acids, and vice versa. Therefore, in the presentinstance, the oxidation of 45 Baum petroleum distillate (i. e., kerosene) should be carried `only to about 20% complete oxidation.- The preferred degree lof oxidation may be controlled by titration, or by observing the incipient formation of the petroleum-insoluble bodies.

The oily mixture obtained according to the above procedure is removed from the oxidizer l through the valved liquid dischar e pipe' 8 into the separatingtank l2, and wased with water. This washing operation has for its purpose the removal of Water-soluble bodies. After the withdrawal of the wash water, sufiicient dilute caustic soda is introduced,

through the valved supply pipe 16, to exactly neutralize the Water-insoluble acids present in the oily mixture and the mixture is agitated, forming thereby a solution of sodium soaps of the carbox lic acids. After the soap solution has settle to some extent a test 1s made to determine whether or not the aqueous soap solution is of such a high concentration as' to hold, perhaps in colloidal solution or suspensiom-any of the unsaponied oils. In

the event that the said soa solution is of such The supernatant unsaponiied oil, consisting usually of from (S8-80% of the total mass,

is drawn off, through the valved conduit 13, to the petroleum distillate supply tank 14 for admixture with additional quantities of fresh distillate, and is again subjected to the oxidizing treatment in the oxidizerl. It is a fact worthy of notice that the petroleum blydrocarbon mixture comprising in part t e material which has already been subjected to treatment does not require the presence of an oxidizing catalyst or exciter of oxidation to eHect normal oxidation, the oxidation proceeding in a manner identical to that observable upon oxidizing a fresh charge of the starting material containing an added exciter of oxidation.

The clear soap solution in the acid precipitating tank 17 is decomposed by treatment with a sufficient amount of a suitable acid, for example sulfuric acid, in a manner substantially as follows: Into the soap solution, agitated by any suitable means (for instance, by a stream' of air), there is introduced gradually, through the valved supply pipe 18, an amount of sulfuric acid sulicient to de compose all of the soap, or slightly in excess of that amount, Thecompletion of this operation may bedetermined by observation, or by the` use of Congo paper or other similar means of testing. When testing for the completion of the decomposition with Congo paper, the reaction should not be considered complete at the first indication' of color change in the test paper, but the addition of acid should be continued untilthe color changeris very strong. By following this procedure the soap is completely decomposed with the production of an oily mixture containing purified free water-insoluble carbox ylic acids and an aqueous solution containing sodium sulfate. The slight excess of sulfuric acid referred to serves to promote a clean separation. After settling, the 4contents of the acid precipitating tank 17 is found to comprise two well-separated layers; the one comprising the oily mixture containing purilied Water-insoluble carboxylic acids having a specific gravity between .945 and 1.0, land the other comprising an aqueous solution containing 'sodium sulfate. The latter solution is discharged through the valved discharge line 19.

The oily mixture thus obtained contains some volatile bodies which might depreciate the value of the product as a softening agent for nitro-cellulose compositions, if allowed to remain therein, consequently it is preferable to remove such volatile bodies. As one mannerin which this operation may be effected, I prefer to subject the oily mixture to vacuum distillation and to a treatment with steam substantially as follows:

The oily mixture is withdrawn from the acid precipitating tank 17, through the valved discharge line 19, into a still 2() wherein it is distilled at a temperature not exceeding about 150 C., under a pressure of from treatment with a rather undesirable polymerization and/or decom position. In general,

l teninga ent,Ihave 10-20 mm. of mercury, and in an atmosphere of superheated steam, air or other suitable inert gas.

Under the above conditions, the said volatile bodies contained in the oily mixture are volatili'zed and carried out of the still 2U under the influence of the partial vacuum created by the vacuum pump 24, condensed 1 in the condenser 22 and caught in the distillate receiver 23. Followingr the vacuum distillation the liquid residue is subjected to rapid current' of steam, in order to sweep out all bodies volatile at the temperature and pressure used, leaving the purified softening agent. De-

pending upon the temperature at which the steam treatment (i. e. sweetening) is conducted, the specific gravity vof the purified product obtained from 45 Baum fuel distillate will be found to be between 1.0110 and 1.0150. i

The vacuum distillation and subsequent steam treatment should be conductedunder such conditions as not to allow over-heating ,of the carboxylic acids, since temperatures of about 160 to 175 C. apparently cause some it may be stated that the lower the temperature to which the oily mixture is raised for the complete removal of all bodies which, at room temperature or somewhat higher., will volatilize overa long eriod of time (e. g., a year or more), the etterthe grade of softening agent produced. Also, it is to be,v noted that the higher the viscosity ofthe finished product the better, for the reason that largerproportions of the softening agent may be admixed with the nitro-cellulose. I

In preparing nitro-cellulose coat `compositions containing the above-described sofbe intro uced in amounts up to 95% of the total composition without detriment, although I prefer to incorporate about Y0-80% .of the softening agent with about 2515% of nitro-cellulose and about 5% of pigiments and filler, depending upon they desire relafound that the latter may tive softness or stiffness of the composition. The economic advantage in the use of compositions containing vthese relatively high proportions of softening agent is especially obvious when it isconsidered that the softening agent is considerably less expensive than either the castor oil-or the nitro-cellulose since it is known that ordinary castor oil can not be introduced into the nitro-cellulose coating composition in an amount exceeding about 55% of the total composition withoutdetriv to castor oil and adaptable for use as a sub- -stitute for castor oil in numerous relations.

While the above-described procedure for preparing the softening agent has been set out as a batch process, itis to be understood that the invention is not restricted thereto, and that the process may be made a continuous or cyclic process with obvious economic advantages. For example, a body of distillate may be subjected to controlled partial oxidation while moving throu h the oxidizer, the reaction mixture containing petroleumsoluble carboxylic acids may be contacted with,-for instance blown in the form of a spray into,-a solution of a caustic alkali, the reaction mixture continuously transferred to a separatin tank from which unoxidized oil and soap so ution maybe separately removed, the unoxidized oil continuously removed from the separating tank and returned to the body of distillate, and the soap solution decomposed and the resulting'free carboxylic acids purified in the revular manner.

While the production of the hereinbefore described softening agent is not restricted to any particular ,theory of oxidation reactions, the following is advanced as being a probable explanation of said reactions:

In regard to the reactions which may take place during the controlled oxidation of petroleum hydrocarbon mixtures by means of air under pressure at reacting temperatures, it is thought that the main primary reaction is one in which theoxygon attaches itself to a secondary carbon atom in the hydrocarbon chain and, in. general, it is believed that the first secondary carbon atom after the primary carbon atom,-in other words, the carbon atom in the -position to the CHa group at the end of anychain or branch-1s the one to which the oxygen first attaches itself.

It is further the opinion, from-many observations, that the oxygen is absorbed without theloss of any hydrogen; in other words, a hydroxyl group is formed at this point, thus forming a secondary alcohol.

The principal reason for assuming that this is the case is the fact that with the oxidation of a given mass of petroleum there is obtained as lhigh as 15% of formic acid and it is believed that this is due to the end hydrocarbon radical being eliminated in the form of formic acid by the oxidation of al ketone formed from the secondary alcohol in which the hydroxyl is attached to the carbon atom. The above conclusion isv supported by the fact that when a secondary alcohol is oxidized it lirst forms a ketone. When a ketone which is a methyl X ketone,-that is,

`one in which the methylgroup is on one side of the CO group and a group of very much higher molecular weight is on the other side of the CO group,such ketone oxidizes in such manner as to leave vthe CO group attachedv to the larger molecule, the CO group thus becoming the carboxylic groupl of the high molecular weight acids and the CH3.

group forming formic acid. The rule in other words is that when ketones are oxidized .the CO group attaches itself to the radical of higher molecular weight and the group of lower molecular weight is oxidized to the corresponding acid containing only the total number of carbon atoms which that group has minus the CO group. i

This view is further supported by the fact that of the oil remaining after removal of all easily volatile and all acid products the greater proportion `forms crystalline compounds with bisulphite, indicating the presence of rather large amounts of ketones or aldehydes but, as before stated, the opinion inclines to the formation ofketones rather than aldehydes because of the very large production of formic acid. When it is considered that one is treating hydrocarbons with an average composition around CMH42 and that one obtains as high as 15% of actual formic acid there seems to be almost no other explanation for the main or principal reaction.

It has also been found that the mixture of acids produced under conditions tending to avoid production of hydroxy acids shows a molecular weight which, in most cases, corresponds to hydrocarbons of about 50% higher molecular weight than those chosen for the oxidation. This may be accounted for in two possible ways. There maybe incipient oxidation in the end hydrocarbons,-that is,

.of the methyl group of the hydrocarbons,-

in such a way as to effect what is known as the Kolbe reaction. If simultaneously, by an atom of oxygen, two hydrocarbon molecules are so oxidized'that the methyl group, in the case of each molecule, loses one hydrogen atom we would have a synthesis immediately of the two hydrocarbon molecules forming one of twice the molecular weight less two hydrogen atoms. The other possible explanation, which woud appear to be the stronger, is as follows: The acids when first formed are extremely liable to further oxidation and as in practically all cases one would have at the other end of a straight chain, or at any other branch, a carbon atom in relatively the same position as the first secondary carbon atom which had been oxidized to ketone and acid whichv also would be oxidized, probably almost simultaneously, to an alcohol. The

acid in one case would either form a lactone n such manner that very large moleculesare formed by the esterification of hydroxy-acids by acids of the same, or higher, or lower, molecular weight, thus forming almost endless chains. Separations by partial precipitation have been obtained from acids which show an average molecular weight of about 360, acids having molecular weights as high y as 800 and, from 'the same mixture there have been precipitated acids having molecular weights as low as 100.- This is particularly true where the oxidation has been carried far enough to form' petroleum-insoluble hydroxycarboxylic acids. This would very naturallly be the case since it is just these acids which one knows are the hydroxy-acids as they show a considerable .absorption of acetyl and we have now proof of their polymerization either through esterization or through polymerization due to the fact that they have the hydroxy-group. This hydroxy group also may readily become a'ketone group, as is readily perceivable. Ketones in themselves are also extremely active; especially, the higher ketones show a great tendency to polymerize. This may be an added cause for the production of acids of extremely high molecular weight. l

An additional fact which supports the idea of ester acids or ketone acids being formed, is that, if these higher molecular weight acids are distilled without too much destruction, there are obtained mixtures of lower 'molecular weight acids and ketones with some small .of an exciter of oxidation,

lecular weight. This would appear to support the'ester acids hypothesis.

This application contains subject matter in common with my applications:

Serial No. 588,073, filed Sept. 13, 1922 now oxidizing gas with a petroleum hydrocarbon mixture in liquid state at a reactive temperature above 100 C. and not substantially above 155 C. and at a pressure greater than atmospheric pressure but substantially not above 350 pounds per square inch, producing thereby oxidation products includingr waterinsoluble, saponiiiable carboxylic acids which are soluble in the hydrocarbon mixture, continuing the oxidation so long VV'as to give a maximum yield of said Water-insoluble petroleum-soluble carboxylic acids while avoiding the formation of petroleum-insoluble acids, saponfying the said acids separating the resulting soaps from the hydrocarbon mixture, decomposing the soaps by treatment with an acid and separating the free acids thus obtained from the reaction mixture, and subjecting the said acids to vacuum distillation anda treatment with steam.

2. Process which comprises contacting a free-oxygen-containinggas with a petroleum hydrocarbon mixture in liquid state at a reactive temperature above 100l C. but not substantially above 155 C. and at a pressure greater than atmospheric pressure but substantially not above 350 pounds per s uare inch, producing thereby oxidation pro ucts including water-insoluble, saponiable carboxylic acids which are soluble in the hydrocarbon mixture, continuing the oxidation only so long as to give a maximum ield of said Water-insoluble petroleum-solu le carboxylic acids while avoiding the formation of petroleum-insoluble acids, saponifyingy the said acids, separating the resulting soaps from the hydrocarbon mixture, decomposing the soaps by treatment with an acid and separating the free acids thus obtained from the reaction mixture.

3. Process which comprises contacting a free-oxygen-containing gas, vin thev presence with a petroleum hydrocarbon mixture in liquid state at a reactive temperature above 100 C. and not substantially above 155" C. and at a pressure greater than atmospheric pressure but substantially not above 350 pounds per s uare inch, producing thereby oxidation pro ucts including water-insoluble. saponifiable carboxylic acids which are soluble in the hydrocarbon mixture, only so long as to ve a maximum eld of said water-insolub e petroleum solu le carboxylic acids while avoiding the formation of petroleum-insoluble acids, saponfying the said acids, separating the resulting soaps from the hydrocarbon mixture, decomposing the soaps by treatment with an acid and separating the free acids thus obtained from the reaction mixture.

4. Process which comprises contacting a petroleum distillate with a free-oxygen-containing gas at a reactive temperature above 100 C. and not substantially above 155 C. and at a pressure greaterthan atmospheric pressure but substantially not above 350 pounds per square inch, in the presence of an added exciter of oxidation, separating the resulting acids from unsaponified reaction mixture residue, mixing the separated unsaponicontinuing the oxidation fied reaction mixture residue with fresh pepetroleum hydrocarbon mixture in liquid,

state at a reactive temperature above C. but not substantially above 155 C. and at a pressure greater but substantially not above 350 pounds per square inch, producing thereby oxidation products including water-insoluble, saponifiable carboxylicvacidswhich are soluble in-,the hydrocarbon mixture, continuing the oxidation-only so long as'to'give' amaximum yield of said water-insoluble etroleum-soluble carboxylic acids while avoiding the formation of petroleum-insoluble acids, saponifying the said acids, separating the resulting soaps from the Ahydrocarbon the soaps by treatment with an acid and separating the free acids thus obtained from t e reaction mixture.

6. As a new product, a material comprising water-insoluble carboxylic acids substantially identical with those obtainable by contracting a free-oxygen-containing gas with a petroleum hydrocarbon mixture consisting of a 4843 Baume petroleum distillate-in liquid state at a reactive temperature above 100 C. and not substantially above 155 C. and at a ressure greater than atmospheric pressure ut substantially not above 350 pounds per square inch, producing thereby oxidation products including water-insoluble, saponifiable carboxylic acids which are soluble in the hydrocarbon mixture, continuing the oxidation only so long as to give a maximixture, decomposingv mum ield of said water-insoluble petroleumsolub e carboxylic acids While avoiding thek formation of petroleum-insoluble acids, saponfying the said acids, separating the resulting soaps from the hydrocarbon mixture, decomposing the soaps by treatment with an acid and separating the free acids thus obtained from the reaction mixture.

In testimony whereof, I aiix my signature.

. ARTHUR W. BURWELL. 

